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Is joining the air force a good way to become an airline pilot?
I've always loved the air force. However, my main goal is to become an airline pilot. Would joining the air force affect becoming a commercial airline pilot?
I am asking because if I join the air force, I am committed to seven years of service. Would this put me behind other pilots? Or, do airlines like pilots with military backgrounds?

I believe Australia has airlines with cadet programs, where you train from no experience to a first officer's slot. Since those come with job offers, that'd probably be the best route.

Thanks cpast, thanks for the fast reply. I'm leaning more towards one of the cadet programs.

Might depend on what you do in the Air Force. If you end up doing food preparation in the kitchen, you won't be any closer to your goal of being a pilot ;) The answer might be different from country to country. Specifying what country you're talking about will help people answer from their personal experience, rather than their personal opinion on a hypothetical situation.

Honestly, every U.S. Air Force pilot I know, who wanted to retire to the airlines, got hired on with no problems.  The ex-Air Force pilots I know have all gotten immediately put into the big planes: A380, 747, 767, 787, etc right from the start.  This is because the airlines know that an ex-military pilot has had some of the best training and experience in high pressure situations.
That being said, in the USA it is very hard to become an Air Force pilot.  You have to contract with the Air Force before they even let you know if you can go to pilot training.  That means, if you don't make the cutoff for pilot training, you have to spend at least 4 years in the Air Force.  If you do make it through Air Force pilot training you have to contract for 10 years after you finish flight school, which means about 12 years from your date of commissioning.  This will take a good 16+ years out of your life, including the time spent in college.  However, you will progress from your first flight all the way to potentially flying F-22s in under two years - a rate of progressing you won't see anywhere else.
Bottom line is, if you don't want to join the military then you shouldn't.  By joining the military you are expected to give your life for people you may not know, or even care about.  That aside, there's no point in spending a minimum of 16 years doing something you don't like, or fighting for a cause you don't support just to become an airline pilot.  If you can find a good airline cadet program, or scholarship, you can become a great airline pilot, it will just take a longer time to progress from one aircraft to another.
Just a little tangent.  That being said, I'm currently an AFROTC cadet, and I had no military background.  I love AFROTC, the US Air Force, and the USA.  I'm currently applying for a pilot slot in the U.S. Air Force, but if I don't make it I would be vary happy taking other jobs, too.  The key is to have small, achievable goals that you can take one step at a time.
I wish you the best of luck.

This answer generally applies to Australia as well (which I believe was where the question was asked before a few edits). I would say that if his goal is to fly an airliner and he won't be happy doing anything else (including ground-based work) the Air Force is a risky move. But if he's attracted to the military lifestyle and all of its demands it certainly will not hurt his future career.

Awesome, thanks for the replies. I've always been attracted to the military ever since i was really young. To be honest as long as im flying i guess it doesn't really matter whether im military or civilian. The thing I love about this site is everyone does care and they put time and effort into their comments. I'll be sticking around so i'll see you guys again then :) Again Sponge Bob and Ben your replies willapplies to Australia as well (which I believe was where the question was asked before a few edits). I  really help me in choosing my career path. Thank You

@Fraser, even if you are in Australia, you can still apply to the Air Force Academy or AFROTC here in the USA, but of course you would be serving a different country than the one you grew up in.

Yeah, I've thought about joining the US Airforce or one of their military branches however from what I understand its not easy for a foreigner to join up.

Actually, the statement You have to contract with the Air Force before they even let you know if you can go to pilot training is not completely true. Joining a guard or reserve unit can provide you with a pilot slot before commissioning. However, most people getting guard/reserve pilot slots already have significant civilian hours. It is possible, though rare, to get a pilot slot straight off the street in a guard/reserve unit

@SpongeBob - AFA and AFROTC comments are actually incorrect unless you hold permanent resident status in the US (aka Green Card); even then you might not be able to attend the AFA due to citizenship requirements. The only way that non-resident aliens in the US can generally enter the US military is through the MAVNI program which is currently only being used by the US Army to help address a shortage of doctors, surgeons, and certain language skills (not translators, just servicemembers who speak the languages). There are also additional visa and physical presence requirements that must be met.

AFAIK, you cannot become an officer in any branch of the US military unless you're a US citizen (MAVNI normally gives citizenship before you're actually commissioned). USAF pilots are required to be commissioned officers, and aren't recruited through MAVNI (we already have plenty of pilot candidates), so you'd have to be a citizen first.

There are advantages and disadvantages to becoming a professional pilot via the military route:
ADVANTAGES:
Lots of multi-engine turbine time, in all weather conditions, day or night using modern avionics.  One of the key things airlines look for in pilots is that kind of experience.  You can build up that kind of time in the civilian world, but be prepared to work several years, first as a CFI, then moving into corporate flying or the regional airlines for low pay and hard hours.*
Flight training is free, once you are accepted into the program.
Experience operating an aircraft under stressful conditions or in combat shows you can think on your feet and can operate unfazed in emergency or dangerous situations.
Good leadership building skills.  Military pilots are officers which is the civilian equivalent of a manager.  You will have other assigned duties in your squadrons other than flying which require you to lead small teams of enlisted personnel in activities related to squadron need ie maintenance, procurement, etc.
DISADVANTAGES:
Lengthy commitment:  It costs Uncle Sam about $2 million USD to train a pilot from entry into JPTS to ready to enter their assigned squadrons, so a lengthy commitment (typically 7 years) is required.
Small number of available slots: Pilot/Naval Aviator/Marine Aviator - especially fighter pilot - are extremely sought after slots and entrance is highly competitive.  Top grades in undergraduate work plus solid leadership skills are a must for a good shot at a pilot slot
UPDATE:  times have changed and there is s high demand for military pilots.  The USAF needs over 2000 pilots right now, including 1500 fighter pilots.  The USN/USMC have similar recruitment shortages.
Stringent academic and medical standards:  Military flight training will not accept people who need corrective lenses and a few other medical ailments can often disqualify people from pilot slots.  It is more strict than what you would find in getting a civilian medical certificate from the FAA.  UPDATE: with the pilot shortages, the military is issuing a lot of waivers for corrective surgery and lacing their standards.  It’s s supply and demand thing.
More demanding / high washout rates:  Military flight training is much more demanding than it's civilian equivalent.  Pilots and particularly combat pilots are selected from the very best available crop.  Instructors are quick to identify slow learners or people who can't grasp the basic fundamentals and weed them out for good reason:  they are likely to be killed in combat or get others killed.  Struggle in UPT, you’re likely to fly tankers or cargo aircraft.  Really struggle and you will likely fly a word processor.  And you are committed to 7 years with that branch of service whether you complete flight training or not.
Civilian Routes to Professional Pilot are available:  There is no reason you cannot become a professional pilot in the civilian world, but it will be more expensive and time consuming to build the hours needed there.
Military commitment:  You are signing on a dotted line to become an indentured servant of the US Government; this includes a declaration to fight and, if necessary, to die for your country.

I would say that joining the Air Force is not a good way to become an airline pilot. Becoming an Air Force pilot is an excellent way to become an airline pilot. However, becoming an Air Force pilot is incredibly competitive. If you are not an Air Force Academy grad, it's even more. They have about 1,400 training slots available and if you don't get one of them, you still have to serve. It's an excellent job and you will learn a lot, but it will put you a few years back in airline seniority.
Also, there is now a push to get flight training largely excluded from the GI Bill (HR 476). If that happens, you lose even that benefit which is great for reducing a large expense towards that airline job.
If you do get that Air Force flying job, then it should not put you behind other pilots. A lot of pilots do it that way and they are well respected.  However, the government is starting to make it more difficult (and expensive) to make the transition. If you end up in a single engine fighter like the F16, it's even more so because you need to get some multi-enging time, typically at your own expense. There are some other requirements as well.
It's a great career and a great path into the airlines but not a sure thing at all.

If it's the USAF and you got a fixed-wing pilot slot, you'd get some multi-time regardless of what you end up flying as advanced flight training is conducted in the T-38 before people get assigned to their respective airframes for specialization. The concern, however, is a valid one as most mainline carriers would expect to see several thousand multi- hours and 100~ in a small, supersonic jet a decade prior is unlikely to be considered sufficient all by itself.


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Does the CH-47 Chinook generate differential yaw as a side effect of generating differential lift?
I have been reading up on the controls of the CH-47 Chinook.  I understand how yaw movement is created not by counter torque but by opposite cyclic on the front and back rotors. What I'm wondering about is adverse torque created when differential thrust via collective is used for pitch control.  If one rotor is producing more thrust doesn't that mean that the increased drag on the rotor will produce more torque than the opposite rotor which is producing less lift?  I understand that the rotors are locked in synchronization so that they can't produce different torque based on their RPM but what about torque created by the different aerodynamic effects on each rotor?  How is would this unintended yaw be canceled out?

Not an answer to your question, but rotors can and do produce different torque even at the same RPM. The fact that they're locked in unison does not imply anything beyond that they have the same speed. Ignoring the possibility of a stall, if one rotor blade has more angle attack the other, then it produces more lift and consumes more power. Consuming more power at the same rpm, means requiring more torque.

Locking them in unison prevents the rotor blades from hitting one another - generally considered a Bad Thing™

What I'm wondering about is adverse torque created when differential thrust via collective is used for pitch control.

Differential thrust between the two rotors is indeed how the control around the pitch axis is achieved for a tandem helicopter.

If one rotor is producing more thrust doesn't that mean that the increased drag on the rotor will produce more torque than the opposite rotor which is producing less lift?

That's correct, thrust and torque are related to each other and in a quadratic way: doubling the thrust, the torque quadruples. The following plot show this quadratic relationship quite well (consider the dots):

(Source - original plot from Principles of Helicopter Aerodynamics by J. Gordon Leishman)
So having two different thrusts between the two rotors generates as a side effect a net torque on the fuselage when seen from above, like in the following sketch where the thrust (and therefore the torque) on the rear rotor is for example lower than the one on the forward rotor, like in a pitch-up manoeuvre:

(Source, modified by me)
How is this net torque counteracted? Simply tilting the two rotors slightly on the sides in order to generate an opposing torque. In our example, the forward rotor must be tilted to the left and the rear rotor to the right in order to generate a counterclockwise torque (in orange in the next sketch) which compensates for the previous net torque by the two rotors (in blue):

This tilting normally happens automatically, being it built inside the control chain of the helicopter, either mechanically or via the stability system.

Wow, great answer. thank you for taking so much time in your answer.

@tavis you're welcome

Love this analysis!  As a former CH-47 pilot, I have to admit to never fully grasping this issue until now.  The effect of this net torque is really only felt by the pilot if the AFCS (Advanced Flight Control System) is off.  In which case you often encounter significant yaw that you have to counteract with the pedals.

@Cargo23: thanks  Nice work you had

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Can Hellfire missiles be used effectively as air-to-air weapons?
Consider the following hypothetical scenario:
An MQ-1 Predator pilot sees an Su-27 closing in from straight ahead for a kill. The pilot prepares to write up his 10th loss of the week when he has an idea: He targets the Su-27 with the laser designator and fires two AGM-114 Hellfire missiles.
Would this work? Can Hellfire missiles be used effectively as air-to-air weapons?

No. A Su-27 won't come from straight ahead in the first place. The fighter will use guns, maybe from six o'clock, but don't count on it.

That's why unmanned fighters are under development.

Why try to target the enemy fighter with the MQ-1 when you can just have your F-22 escorts chat with them instead? "He flew under their aircraft to check out their weapons load without them knowing that he was there, and then pulled up on their left wing and then called them and said ‘you really ought to go home.' " Not a good day to be an Iranian F-4 pilot.

In this situation I'd just turn on my rainbow designator and fire a heat seeking unicorn.

While I can't say that I know the too much about Hellfires, the aiming capability appears extremely limited for any air-to-air combat.

The range is bad: ~8km (compared to ~35km for a 'proper' Sidewinder). Covering this does not take many seconds for jets travelling in opposite directions. I'd imagine you might be able to get a helicopter if you're lucky.
I'm incredibly doubtful that a sensible lock on any aircraft could be achieved from a Predator. Bear in mind that you only have a camera on the bottom, so you've got huge blind spots.
You got a fair bit of satellite/communication lag, in the range of 0.5 seconds either way to get any response. More likely that your opponent has already got you by the time you understand what's going on.
The majority of the Hellfire missiles appear to require a constant lock to seek its target; some can continue on autopilot with limitations if it were to lose it. Again, sustaining a lock with that setup does not have a good outlook.
Remember that the Su-27 has countermeasures (such as flares) to protect itself.

Flares divert Heat seeking missiles, They won't help anything against other guidance methods like laser, radar or Optical.

Actually, hellfire missiles have been used as air-to-air missiles, albeit only once.
On 24 May 2001, an IDAF AH-64 Apache used two hellfire missiles to shoot down a Lebanese Cessna 152. This is the only known use of hellfire missile so far as an air-to-air missile.
However, it is doubtful if the missile could be employed against a extremely maneuverable target like the Su-27. The AGM 114 is basically a anti-tank missile and not suited for use against aerial targets. The Cessna 152 was piloted by a student pilot and in any case had little maneuverability.
Another issue is that the laser designator has to continuously point at the aircraft through out the guidance phase, which is very difficult in the case of a predator against any fighter aircraft.
Also, the range is poor. All in all, unless the pilot is extremely lucky, a predator is not going to get a Su-27. Maybe a helicopter from its blind spot though.

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Why do VTOL aircraft (F-35 or Harrier) have only one engine?
Why do VTOL aircraft (F-35 or Harrier) have only one engine? Is it because it is simpler and less expensive? Or what are the reasons?

In aviation, the answer to the question "why is there only one" is nearly always because "that's all it needs".

In government, the answer to the question "why is there only one" is nearly always because "that's all there was money for". Many F-16's were lost to single-engine failures. Canada expected this and bought the twin-engined CF-18 instead, but not all countries could spare the up-front expense.

I'll make this a comment since it's not enough info for a full answer, but a single-engine craft is much more stable in an engine failure. If the single engine fails, the craft remains right-side up allowing easy ejection. In a twin-engine craft, the most obvious arrangement of lift vents is similar to the Harrier's, but one front and one back per engine. If an engine fails in that configuration, the aircraft will roll, hard, making ejection risky or fatal. Similar issues of redundancy plagued the Osprey's designers and contributed to the most complex rotor-driven aircraft in the U.S. arsenal.

The nozzle mechanism looks kind of heavy?

VTOL aircraft can have more than one engine. It is just that the design process of the Harrier and F-35 led to a situation where only one engine was required.
The main challenge in any VTOL aircraft is to have the engine produce thrust in two different phases of flight: during cruise and during takeoff/landing. This basically requires the powerplant on the aircraft to have two different characteristics at those two phases, because

The direction of the thrust vector is different in TO/Landing and cruise
Amount of thrust required is different; for vertical TO, the thrust should be more than the weight while in cruise, the required thrust is (comparatively) pretty low.

A number of approaches have been tried to solve this problem:

Takeoff the aircraft vertically (aka the tail sitter), like Ryan X-13 Vertijet, and then transition to horizontal flight. However, one major problem is the pilot has severe disorientation problems during transition
Put extra fans, like the Ryan XV-5 Vertifan. The problem was the large (wing) area taken up by the fan and weight penalties. Ironically, a similar concept has been used in F-35
Put extra engines specifically for vertical lift (aka the 'Rolls Royce Concept'), used in Dassault Mirage Balzac. Though this offered (theoretically) better safety, the weight penalty was too much.
Optimise the main engine for cruise and deflect the thrust for takeoff and augment with (small) lift engines (aka the tiltjet concept), like the German EWR VJ 101. This reduced the weight penalty and complexity, but reduced safety in the event of an engine failure.

In order to avoid the weight penalty, the best approach is to have no extra engines at all, with the thrust deflected down at take off and landing. This was called 'vectored thrust' (a term attributed to Theodore Von Karman). This concept was tested in the Bell X-14, which had fixed eingines and thrust vectoring vanes that deflected the exhaust to achieve vertical lift.

Source: history.nasa.gov
In case of the Harrier, the engine, the Bristol Siddeley Pegasus was first developed (as BE.53) and the Hawker aircraft decided to develop an aircraft around it.
During the design proces, the aircraft was redesigned around the Hawker modified BE 53 which the rear jet was split into two, like the Hawker Sea Hawk, which had a similar arrangement. This lead to the 'four poster' thrust vectoring system in the  Harrier.

Source: www.aerospaceweb.org
This is the reason, the Harrier had a single engine.
The case of F-35 is different. The F-35 was designed to replace aircraft operated by a number of US services, and as such had conflicting design requirements. At one end, the USAF wanted a conventional fighter while the USMC wanted a VTOL aircraft. The USN requirements were somewhere in the middle.
Lockheed designers decided that the best way to meet these requirements is to have a separate fan for lifting the aircraft in VTOL, which can simply be eliminated in the USAF and USN variants. This led to the lift fan arrangement (eerily similar to the Vertifan arrangement).

"F-35B Joint Strike Fighter (thrust vectoring nozzle and lift fan)" by Tosaka - Own work. Licensed under CC BY 3.0 via Commons.
So, in case of F-35 the use of a single engine was the best way to meet the requirements. The engine used, the Pratt & Whitney F135 is the most powerful fighter jet engine in service, which helps in making F-35 the first supersonic VTOL aircraft.

Form your answer I can summarize that there was 2 reasons: weight and size. But F-18 has 40.4 fit in width, and F-35 only 35 ft, and 2 engines probably means 2x vertical thrust. So I can assume that a fuel consumption because of weight is the real reason.

@RS Are you talking about the wingspan? In that case, please note that the F-35 has heavier than the F-18 and the thrust produced by the F135 in F-35 is greater than the thrust produced by both the F404 engines of F-18 combined

@RS not only weight: keep in mind that F-35Bs are designed to land vertically on amphibious assault ships, so, unless the F-35Bs were designed with two engines, each one capable of lifting the entire weight of the aircraft, having two engines is completely pointless.

Many VTOL aircraft have two engines: Bell 212, EC135, MH-53. There is even one with three engines, the CH-53E. Yes helicopters are aircraft too. These have all engines drive one propulsion device, and that conveniently means there is no change in the location of the thrust point if an engine fails.
As @Ryatt Broach mentions, the V-22 has a complicated system that allows one engine to drive two rotors, and so does the CH-46.

The Harrier could have two engines blow in the one propulsion manifold, and enjoy a bit of redundant propulsion safety as well. But there are a lot of tradeoffs in aircraft design, and the Harrier did pretty well.

The mighty Phrog lives, if only in our hearts ...

Don't forget about the V-22. The V-22 has had problems in the military because two engines may cause different amounts of thrust in each engine, So it may cause a problem.
For example a sudden loss of thrust on one side due to a mechanical issue, surge, FOD, etc. The attitude may end up in a position that does not favor an ejection.

This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review

@J.Hougaard I don't quite understand your flag here. Why don't you think this answers the question? As I read it, the answer here seems to be "because asymmetric thrust can cause big problems during VTOL operations, as the V-22 has demonstrated."

The V22's two engines are connected together via a driveshaft that runs through the wing, to address that very situation. Doesn't matter if the power output from one engine varies from the other, the single driveshaft connecting them insures that there will be no asymmetric thrust. Also, one engine can supply enough power to operate both rotors.

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Why is the C-xx aircraft series used by multiple manufacturers?
Lockheed Martin C-130J Super
Hercules
Boeing C-17 Globemaster III
Cessna C172
Unlike A and B, why is C used by various manufacturers? Are there any copyrights for such alphabets used in aircraft model name?

Unlike A and B: if you think all Bs are done by Boeing, I would take a look at the B-2. And for As, a quick look at A-6 and A-10.

As for B, you are forgetting all Beechcrafts.

I'm wondering if you're confusing the military designations (A10, B2) with commercial model numbers (A300, A380) and atc abbreviations (B737, B777).

@TomMcW yes I am (was) ..!!

That's why I always laugh when some private pilot is going on and on about their flight in a "C-172"-- yeah, whatever, like you are flying some big transport.  Ditto some guy talking about his time in the "B-747" or whatever.  Pilot to bombardier, prepare to begin the bomb run, hope the passengers don't mind the flak too much ...

Trademark law is a tricky thing: Two companies can use the same mark (name) as long as they are in different areas of business - like Apple (the computer company) & Apple (the  record label that published The Beatles) (which got incredibly complicated when iTunes happened and the computer company entered the music business).
Even within the same business area commonly-used names can overlap. A good example of this is the Cessna 140 and Piper's Cherokee 140: they're both referred to as "a 140" in their respective pilot communities, but their manufacturer model numbers are different (Cessna's model number is 140/140A, Piper's is PA-28 140).

None of that applies in this case though, because the names you're looking at don't come from the manufacturer:
The C in US military aircraft models (C-130, C-17, C-5, etc.) specifies it as a Cargo aircraft (Similarly F is used for fighters, A for attack aircraft, and B for bombers).  Combined designations also exist (e.g. the AC-130 Spectre, a Lockheed C-130, which is subsequently converted to a weapons platform by Boeing).
The aircraft designations in these cases are assigned by the military, not the manufacturer, and they may not match the manufacturer's designation (though for aircraft designed exclusively for military service they may).
 Several manufacturers produce aircraft in each category (e.g. the F-14 was a Grumman aircraft, while the F-16 is made by Lockheed/General Dynamics), and many manufacturers produce aircraft in multiple categories (Lockheed for example).

The US Military Trainer version of the Cessna 172 is designated as the T-41 Mescalero, but it is clearly recognizable as a (mostly-standard) Cessna 172.

The use of C172 for the Cessna 172 is also not the manufacturer's model designation: It is the ATC aircraft type code and is used as a matter of convenience when talking about a generic aircraft (e.g. "Your typical Cessna 172"). Cessna light aircraft models are generally designated by the family number (150, 152, 162, 172, 182...) and a variant letter or letters (172S, 172RG, etc.), which indicate a specific set of aircraft within the general 172 family that share some common characteristics.

Don't all the C172s share a type certificate?

Also Apple and Apple fought it out in court, especially since Apple Computer is now in the Music Business. https://en.m.wikipedia.org/wiki/Apple_Corps_v_Apple_Computer

The reason 'C' is in the names of C-17 Globemaster III and C-130J Super Hercules is because US DoD follows the 1962 United States Tri-Service aircraft designation system.
As per this system, all aircraft are assigned a Basic mission code, here 'C' for Cargo (Transport). This is given by the DoD and bears no resemblance to the civil aircraft (Company) name.
For example, the USAF and US Army operate a variant of Cessna 172, which is called T-41 Mescalero.
The Cessna 172 may be called C172 by some users, thought there is no 'official' name as such for the Cessna 172 Skyhawk.


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Why don't Russian aircraft sell as much as their European/American counterparts?
Are there any reasons other than political why Russian jets don't sell?
For a case study, let's compare Sukhoi Superjet and Mitsubishi  Regional Jet. Despite being delayed several times, Mitsubishi has secured more orders than Sukhoi. Similarly, Embraer and Bombardier aircraft sell much more than the Sukhoi Superjet. Many new airlines continue to go to with Embraer and Bombardier. Despite promising lower running, maintenance, purchasing costs, why doesn't this aircraft secures orders?

Very similar

They aren't nearly as good?  Sometimes you just get what you pay for.

There is a lot to be said for sticking with an aircraft you already have trained maintenance personnel, spare parts, and pilots for...

Reliability reputation aside, you really can't ignore the political reasons. To put it mildly, Russia has strained its relationships with many of the other countries that buy a lot of airplanes lately. When you're buying an aircraft that you'll likely be operating for a decade or two, the risk of your parts supply chain suddenly being embargoed if the situation escalates further is not a good one. Along those same lines, Boeing, Airbus, and Embraer are probably less likely to stop existing over the next couple of decades than most of the Russian manufacturers.

There are two kinds of reputation, to make matters worse. Even if Sukhoi establishes a good operational record for, say, ten years, as an operator you'd still not enjoy being marked as 'flying Russian aircraft' in the news or  Internet discussions.

One might as well ask why Lada sells much less cars than Toyota despite having lower costs.

Note that Bombardier and Embraer aren't European or American (unless you're taking "American" to mean "from anywhere in the Americas")

Was waiting for someone to point that! Even Japan isn't American or European..

@RonBeyer: Which, of course, explains why Russian airlines are buying up Boeings and Airbusses as fast as they can get their hands on the necessary cash, and scrapping their Ilyushins and Tupolevs and Yakovlevs...

If you take out the political angle (which is by far, the most important), there are a number of reasons for this.

Basically, the Russians have a serious image problem. Russian (and Soviet) aircraft have a reputation for poor quality, reliability and safety issues. This will take a long time to fix. In contrast, Japanese have no such problems (In fact, the MRJ boasts of 'legendary Japanese reliability')
It is not easy to make airlines switch from an existing aircraft. Most airlines have a huge system built around the aircraft they operate (In fact, quite a few regional carriers operate only a single aircraft type). It would take enormous amount of investment in time and money to shift to a new aircraft and it would take a large incentive for them to put their eggs in a new basket.
US is probably the most important market at present and operating there gives other airlines a lot of confidence to buy the jet. If you see the orders for MRJ, most are from US (In fact, almost all orders are from either US or Japan). The Superjet, in contrast, hasn't even applied for FAA certification as far as I know.
Promising and delivering lower costs are completely different things. Airlines are more prone to believe companies that have a proven track record of manufacturing civil aircraft than a newcomer.
The Superjet is the first airliner to be developed in Russia since the end of cold war. As such there are questions about its industrial capability and quality control processes. Mitsubishi, on the other hand is engaged in a number of aircraft projects (it makes more than a third of 787 structure).
Sukhoi has to build a supply chain and support system from scratch (Superjet has a number of foreign components). Again, in the extremely cost sensitive airline industry with tight schedules, there is a perception that the Russian aircraft will not be supported as well as their western counterparts (For example, Boeing boasts of a >99% dispatch reliability for 737)

The quality is not just an image problem - the comments from friends that have flied on Sukhoi Superjets are rather one sided; no matter if their flight and operational cost properties meet expectations, the plane interior build quality simply isn't that good, even economy-class fliers of the first world feel that it's inferior to other (incl. much older) planes and would prefer airlines that use something else than the Superjets.

Quality control is really hard - even Boeing dropped the ball with the 787. It's not really a surprise that Sukhoi struggles too.

@Peteris, interior build is not an essential characteristic of the plane. Different airlines may order different cabin layouts with more or less leg room, cheaper or better materials, etc. There are some plane characteristics that make flight uncomfortable no matter what, for instance noisy engines. But as far as I recall, SSJ engines are quite usual in noise.

Image and trust are huge - passengers (even frequent fliers) are often nervous aboard aircraft, but they've learned to trust the Airbus and Boeing brands.

@JonStory And, yet, a huge number of shorter distance flights within the US and Europe are on planes made by companies such as Embraer, Bombardier and Fokker. It's clearly not necessary to fly Airbus or Boeing to maintain customer confidence.

Well for one thing, in Europe the vast, vast majority of even shorter routes are on 737/A320 series aircraft: but there's also the point that Embraer, Bombardier etc have become trusted. Russian and Chinese manufacturers (rightly or wrongly) are generally considered less high quality. It's brand perception, and it isn't always logical. Still, most people would choose a Boeing over a Bombardier

@JonStory nah.  Passengers see that a reputable airline is using the craft, and that's good enough.  (The reputable airline has it's reputation, for one, because it chooses good airplanes.)

I think reputation has a lot to do with this, I'm sure there are Russian aircraft out there that have outstanding safety records, but media has focused on some high-profile accidents as well as shoddy/corrupt government.
Also, certification is probably the other barrier, the bigger the aircraft the more expensive it is to certify it for various civil aviation authorities.
I think EASA and FAA have lots of rules/ standards worked out among themselves, but I don't think the Russian authority is well integrated.

Interesting question: I remember having read long time ago, that Russian-built airliners tended being underpowered respect to their western counterparts, this resulting in slow climbing and other operational difficulties for air-traffic controllers.
Also, the USSR airplanes' instruments were metric; besides pilots say that feet are a bit more accurate in estimating height for things as precission landings, one meter is around three feet, also a mile is a minute of arch, no match between a km and arches, some problems resulted, for example, in places where metric units were used for fuel. For those having a local way for measurement, it's easier adapting to using it plus another more universal system than the reverse, from the general to the private, habitudes are hard to change
A Mars probe crashed when somebody mismatched metric and 'imperial' units in the software, an airliner had to make an emergency landing in an abandoned airstrip, this won the pilot an award, as he managed the no engine, gliding approach at a too high level, by sliding on the side.
The reason of this commercial jet running out of fuel was a mismatch between fuel supply units.
They said also that USSR jet engines were more fuel thirsty than their counterparts, perhaps due to the lack of access to the rare elements used for high temperature and stress alloys, this limiting the efficiency of engines.

The incident you refer to is known as the Gimli Glider, which was an Air Canada Boeing 767. Furthermore, you might want to use the occasional . or newline to make your answer more readable

Those "British units" were U.S. gallons, which aren't the same as British gallons, which aren't used any more (except that car fuel consumption is always quoted as miles per gallon, even though fuel is sold by the litre).

Using feet for landings is really not important: 500feet/150metres, 50 feet/15 metres... in an aircraft you're travelling fast enough that you're only accurate to 10 feet/3m at the best of times, and even then only for a moment. "100, 50, 40, 30, 20, 10" is not really much different to "30, 15, 12, 9, 6, 3". That's not to say that changing wouldn't risk problems, but once people are used to it, it's just as accurate.

@JonStory And the feet-vs-metres thing can't be anything like a deal-breaker, since there are plenty of Airbus and Boeing planes in service with Russian and Chinese carriers.

As far as I know, most modern airliners have the ability to display either metric or imperial units, anyway.

@JonStory The problem is not so much landing as altitudes. Altitudes that are even multiples of 1,000 or 500 feet are convenient. Using metric would mean either than the numbers are nasty or that the vertical separation is much more (or much less.) Multiples of 150 or 300 would be annoying to deal with.

That's still nonsensical. The altitudes wouldn't necessarily match up exactly but you can easily use 300m of separation just as well as we currently use 1000ft. You fly at FL 80 and I'll fly at FL 83 instead of 260 and 270. Again if we used mixed it could be a nuisance, but not if everyone in one airspace used the same scheme.

About measuring units, I was told about the convenience of feet over fractions of meter some 25 years ago by a former jet fighter and then airline pilot, but situation may have changed

@Urquiola, multiples of 10 are slightly easier than multiples of 3, but you can quickly learn those too if you use them. But it's totally irrelevant regarding plane types—no matter what plane you fly, you fly in metres in China (and some other Asian countries) and in feet anywhere else. Except Russia where you currently fly in metres below transition, but in feet above. In either case, your plane will display what you need.


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When a bomber releases a huge payload of bombs, why don't they collide with each other in mid air?
Below given are images of bombers releasing many bombs at the same time.
Why don't they collide with each other?

I'm sure it's happened, I don't see why it would matter much if they bumped occasionally.

Thanks for asking this - for some reason I just imagined a bunch of bombs just piled up on the floor of one of those planes, and then they just let them go at once. ...makes infinitely more sense (but is a lot less fun) that there's a system and each bomb is placed carefully in releasing mechanisms instead.

"Below given are images of bombers releasing many bombs at the same time." – They are clearly not releasing them at the same time, otherwise, they wouldn't be at different altitudes.

Indeed they do, or at least did.

Because there's a lot of engineering effort to make sure the bombs are cleanly and safely released from the aircraft (safely, that is, for the aircrew, not for the recipients). Aside from the safety issues, it is also necessary to ensure accuracy.
The concern is in the first couple seconds after release when the bomb is moving through the air surrounding the aircraft. Once in clear air, gravity and aerodynamics keep them separate.
Much of it is controlled by the release sequence. If you look at the B-2 photo you can see that bombs are released in a left-right and alternating between the front and aft racks to maintain separation.
The USAF SEEK EAGLE Office is responsible for ensuring compatibility between the weapons and the aircraft.

It also maintains aircraft trim; wouldn't want to e.g. release all bombs on the left side first, as the aircraft would pitch to the right, or all bombs in the rear first, as the aircraft would dive.

If you’ve ever parachuted from an aircraft you’ll know that although you might expect to float gently away into the air, you do in fact drop like a brick.  Bombs are typically released in a controlled manner and so they will tend to separate vertically as they fall.  Given the significant weight of a bomb it’s most unlikely that there would be enough turbulence in the air to cause two bombs falling side by side to touch.

Even if some bombs collide, this would happen laterally with relatively little lateral velocity compared to high forward velocity of the bombs. One could safeguard by arming the bombs some seconds after they have been released.

@DohnJoe Aren't most modern bombs set to blow based on altitude rather than impact anyhow?  You get more bang for your buck by blowing up slightly above the target rather than directly touching it.  So there's little chance of the bombs blowing up while still close enough to the bomber to be a problem (unless it's flying really low, which just seems like a bad idea in general if there's the possibility of people on the ground shooting back at you...)

@DarrelHoffman it probably depends on the objective.  While airbursts are best at spraying soft targets with shrapnel, if you're trying to destroy buildings above ground you want to penetrate and detonate inside the building.  If you're going after underground bunkers or just trying to make craters to impede movement you want to penetrate into the ground before exploding.  The same is true of armored vehicles, you can damage external equipment with a near miss; but to actually destroy a tank you need a direct hit (and either a guidance system or a lot of luck).

@DohnJoe, the delayed arming you describe has been standard practice since at least World War II, and probably since World War I.  (The common mechanism in WWII was a propeller-driven screw on the nose of the bomb; today, it's probably a pressure sensor of some sort.)

@DarrelHoffman Dohn Joe is talking about arming the bomb, which has to happen before the fuse (airburst, impact, delayed etc.)  can trigger it

There is plenty video material on youtube where it is shown that the initial release pf the payload is not simply about gravity. During the first second or so the it is falling through the airstream disturbed by the aircraft, sometimes resulting in rather spectacular trajectories. Therefore Gerry's anwer is more accurate. It's not just about dropping them in a sequence, a lot more has to be fine tuned to make a safe release.

Then there is always the trusty Intervalometer which controls the rate or interval at which bombs are dropped.

The intervalometer generates electrical impulses that actuate the bomb release units. It may be set fore either selective or train release of bombs. When set at SELECTIVE, the intervalometer generates a single release impulse each time it receives an impulse from the bombardier’s firing switch or from the bomb sight. When set at TRAIN, the intervalometer provides a series of evenly spaced impulses. The number of impulses (up to 50), and therefore the number of bombs dropped, is controlled by a dial setting. The impulse frequency can be varied from 2 to 20 per second; it is controlled by matching two dial scales, one of ground speeds and one of distances between the impact points of successive bombs. When the desired spacing is matched with the actual ground speed of the aircraft, a small computing unit automatically sets the proper impulse frequency in the intervalometer.

https://www.eugeneleeslover.com/USNAVY/CHAPTER-23-C.html
https://aeroantique.com/products/bomb-release-control-intervalometer-type-an-b3?variant=24795701191

Bombs aren't just laid together in a bomb bay and dropped out of the bottom of the bomber. They are connected to a launcher, like the Conventional Rotary Launcher in the B-52 (google that for nice pictures), that times the release of bombs to minimize any chance of overlaps during the actual launch process. In addition since the bombs are all the same size and weight and have the same aerodynamics, they tend to maintain the same relative distance from each other once they're launched because there is no difference in the forces acting on each bomb. If a gust of wind blows one bomb sideways, it blows all the bombs sideways the same amount, because they all have the same size and weight and aerodynamics.
And finally, on the modern battlefield bombers are no longer used for carpet bombing like in the pictures you posted. Instead they are dropping precision JDAMs onto exact targets marked by spotters on the ground. These are conventional bombs with fin kits that guide them directly to a designated target. Unless multiple bombs are being sent to the exact same target, they're going to diverge after being dropped from the bomber as their fins guide them towards their specified targets. The end result is, if the guys on the ground called for five buildings and a fortification to be bombed, there's going to be six bombs dropped, all going in slightly different directions, not a whole string of bombs carpet-bombing an area.


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How does the fly-by-wire on the new F/A-18 Super Hornet work and what is it maintaining?
I am trying to replicate the fly-by-wire (FBW) system of the Super Hornet for a game called SimplePlanes. I was wondering if it is maintaining a certain $g$ number, turn rate, angle of attack, or a mix of everything. And, does anyone an equation that can replicate this?

In your simulation, does the pilot have any input?

@MichaelHall SimplePlane is a game in which you fly a simplistic aircraft. So yes, you do have normal pilot controls, such as stick inputs, throttle, flaps etc.

My point is that complex FWB computer wizardry needed to keep a marginally stable aircraft controllable isn't needed for simulation.  Just make it do what the (simulator) pilot commands it to do.

@MichaelHall I think you are right that you don't need the complexity, but the question is not asking for that. The question is what is the FBW trying to maintain? The pilot is commanding the setpoint, and the FBW is trying to match the aircraft state (or state derivative)  to the setpoint. So what is the pilot's stick input commanding:  is it g, pitch, pitch rate, turn rate, roll,  roll-rate etc. To mimic this in a simple simulation you don't need the complex FBW wizardry, but you still need to know what the FBW is striving to achieve.

@DeltaLima, and the point I was trying to get to in my question is that manual mode isn’t trying to “maintain” anything. It responds to continuously varying stick inputs from the pilot and causes the airplane to maneuver just as a stable, non-computer controlled airplane would. Unless the question is about autopilot, it doesn’t make sense as written.

@MichaelHall Surely the FBW is trying to maintain something in manual mode. Why else would you have FBW? How does the FBW respond to stick inputs? If I put the stick neutral, what does it try to do? Keep the elevator neutral, maintain 1 G? maintain constant pitch? constant pitch rate? What if I pull a little bit: proportionally move the elevator, maintain a constant G > 1, maintain constant pitch >0, constant pitch rate >0. The relation between the stick input and what  control surfaces are doing is in the hands of the FBW, even if you are flying manually. The FBW control mode/law  is key here

@DeltaLima, there is a time component to this; when you are maneuvering aggressively nothing is constant for long…. Anyway, in a simulator game there is no need to model real world instability, then model the correction.  Just make the control inputs cause it to fly like any other normal plane.  This is an “XY” question.

@MichaelHall I think you have a wrong concept about a simulator plane and computer-controlled aircraft. Controlling an airframe via a computer does not "magically" eliminate any dynamic the underlying airframe has. On the other hand if your simulation is setup to "just make it do what the pilot commands it to do" feels very very wrong to the pilot. There is a reason why in real aircraft simulators you go through all the trouble of replicating the FBW control in conjuncture with the aircraft.

@DeltaLima You are right, it depends on the mode. Pretty much all aircrafts equipped with FBW (except for these with an unstable airframe) have a least a direct mode in which the pilot directly commands the deflections of the control surfaces. The next higher mode up is most of the times one which I describe in my answer. If tuned correctly, such a mode is employed throughout the envelop of the aircraft. The next higher mode up are autopilot functionalities... So to answer your question, in most cases it is rate feedback, or nz feedback or a mixture.

@U_flow, if the OP were creating a “real aircraft simulator” I would agree with you, but it isn’t for training Naval Aviators. It is for a simple game. Gamers aren't going to notice or care whether the underlying code replicates the FBW computer, hydraulics, or pushrods and cables, they just want something that looks and flies like a Hornet. FYI, years ago I purchased an MS Flightsim add-on that included the A-4 Skyhawk that has a 720 deg/sec max roll rate. It rolled like a 747 in prestall buffet. That felt very wrong to me, but your average gamer might not even pick up on something like that.

@MichaelHall You have a valid counterpoint, but still, there is a difference between no dynamics at all and something designed to handle nicely. You would be suprised of how good handling qualities contribute to a nice "playability" of simulators.

The NASA paper 'Simulation Model of a Twin-Tail, High Performance Airplane' contains a complete set of control block diagrams for simplified version of the actual OFP v10.1 control law obtained from MDC Report A4107. You can code it line by line according to the graphs. This is the best publicly available source for F18 flight control laws.

The F/A-18 relies heavily on computerized control to achieve a number of objectives.
These are (without claiming completeness):

Good handling qualities
Spin resistance
Acceptable High Angle-of-Attack flight and maneuvering characteristics
Avoidance of Adverse yaw
Avoidance of Proverse yaw
...

How these objective are achieved is described in a pretty detailed paper about the F/A-18 Flight control system available online.
Some key (and pretty standard) concepts are the following:
Longitudinal (Pitch) Control
A very standard way to treat the pitch control is to use vertical acceleration feedback ($n_z$) for high-speed and pitch rate $q$ feedback for low-speeds. This is done as pilots judge how much their aircraft pitches at low speed by how much the horizont moves, and at high speed by how much acceleration they feel (remember at higher velocities you feel much more acceleration then you see the horizont move...)
The formula would be
$$ u_x = K_\text{p} e(t) + K_\text{i} \int_0^t e(\tau)$$
whereby $e(t)=d_x - n_z$ ($d_x$ is the pilot input) for high speed and $e(t) = d_x - q$ for low speed. In the intermediate speed range you have a blending of both of these errors. The exact gains for $K_p$ and $K_i$ are also speed dependent and certainly not publicized. They also include special considerations for high AoA which was important at that time, however for a game called simple planes, that perhaps makes no difference...
Lateral (yaw) control
For lateral control, normally you aim at $\beta=0$ whereby the pedals control how much $\beta$ you build up. Again that is goverened over PI-controllers whereby the gains are scheduled on basis of the velocity. Again the paper describes special spin recovery schemes and anti-adverse-yaw implementations. You will have to decide yourself if you want to implement something like this
Roll control
Here, I would simply govern the roll rate $p$, again with a speed-scheduled PI controller
It is worth mentioning that the implementation of a realistic controller relies heavily on a realistic flight model. Therefore if your flight model is simplistic, then your FCS implementation can also be simplistic, but do not expect a high level of fidelity of the overall system. However a realistic FC can be a lot of work to tune, implement and test, so keep that in mind.

...if it is maintaining a certain g number, turn rate, angle of attack, or a mix of everything...

A mix of everything. The computers adjust the active flight controls for:

Providing artificial stability of the airframe. An aircraft is most manoeuvrable if it wants to change direction by itself already, which would require constant small inputs from the pilot in order to maintain flight direction. Not a good situation for human handling, the computer has no problems with it though and can artificially create the stable feel for the human.

Limiting the forces on the structure to the maximum design limits. Above image is a still from this video, depicting the limiting manoeuvres of an F-16. Active fly-by-wire limits the maximum g-load on the airframe, without having to limit the all-moving-tail area or its maximum deflection angle.

And, does anyone an equation that can replicate this?

A single equation I don't have unfortunately. There would be at least 6 required for each degree-of-freedom of the aeroplane, each one with quite a few coupled inputs. And the constants in the equations vary from aeroplane to aeroplane and I don't reckon that are published anywhere.


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Has an airplane ever been launched from a train?
Presumably helicopters have landed and lifted off railroad flat cars.
Has an airplane ever been launched from a train?

(my artwork)

F-84 during project ZELL testing (info provided by jwenting)

That looks too steep, you’ll launch into a stall. Pretty much you want it flat and pointed in the direction the train is traveling. And a heckuva lot of chains to hold it down before takeoff.

Has a kid ever releasesd a balloon from a train? I would believe someone once did.

Depends on what you mean by "train" and "airplane": NASA Considering Rail Gun Launch System to the Stars

I don't really see an operational need for such a system, now or in the past. A catapult launch from a train like that should be no harder to accomplish than from a rolling, pitching, cruiser in the north Atlantic, which was done regularly during WW2, except that there's far less room to work on the aircraft as trains tend to be rather narrow, more so than a seaplane hangar on those ships was.

@jwenting There are two important differences: 1) trains are usually segmented to get round bends, so the limit on runway length is harsher than on a carrier; 2) a train can't turn into wind. I agree about it being a bit pointless.

@DanHulme I'm not talking about carriers, I'm talking about catapult rails installed on transport ships, cruisers, and battleships to launch floatplanes. A system similar to those could be installed on a train and needs no straight track. They usually didn't bother steering into the wind either, but shot the plane over the side with a prayer to the gods of war that it would fly.

Where would it land?

The first photo clearly is a fake. The carriage is from a railroad gun and the airplane photo has been pasted in.

I can't find any evidence of train launch, but recall that in Douglas Baders autobiography he flew a Tiger Moth alongside of a train, remaining stationery relative to the train as the stall speed (flying into a strong headwind) was slower than the train. Given a TGV or similar trains can exceed 250kmh, world theoretical be possible for a light aircraft to take off without a catapult. @Michael Hall, not trying to answer a question raised in a comment, but the fighter aircraft ditched at sea. CAM ships also steered into the wind when launching fighters https://en.m.wikipedia.org/wiki/CAM_ship

@MichaelHall in the case of ship launched aircraft, they'd typically land in the water close to the ship to be hauled back aboard by a crane (or to sink, with the pilot being recovered by one of the ship's boats). In case of project ZEL and similar systems, anything flat and long enough, or the pilot'd eject close to friendly forces.

@jwenting - Absolutely true about ships recovering aircraft from the water. As an interesting side note some Japanese subs carried recon aircraft that had no gear or pontoons so the pilot had to 'crash' next to the sub to be recovered (it was strictly a one way trip). Americans and Germans also had sub aircraft but I think they were all recoverable . Anyway, CRASHING apparently is an acceptable military option!

@jwzumwalt British launched Hurricane and Spitfire fighters from freighters using catapults before there were escort carriers for Atlantic convoys. They too had to crashland next to the ship and the pilot was fished out of the ocean, if he lived long enough.

Not a train, but project ZEL comes closest to what you're looking at.

During the 1950s the USAF had the idea to launch combat loaded jet fighters from inside nuclear hardened buildings and caves using a short launch rail to guide the aircraft and large rocket bottles strapped to it.
Wikipedia article
The idea was to have a fighter capability after an initial nuclear attack. I had an old VHS tape about the project, it was impressive and scary what they did.
For the initial testing a launch system was built onto a heavy truck, an F-100 mounted on it using a crane, and the pilot would get in and be shot into the air by remote control.
Later the ramp was built into a modified Matador or Mace cruise missile launch bunker, the tail clearing the roof by just inches as the F-100 was launched in a massive cloud of black smoke.
The program was eventually abandoned, but no doubt provided a lot of information about structural integrity and forces inside rocket silos.

It's not a train, but Brendan O'Brien (with the O'Brien Flying Circus) has an act where he lands a Piper Cub on a moving trailer, towed by a car. There are some YouTube-clips showing this, including a take-off (around 1:50). Regarding your earlier comment on 'as close at it gets': I think this is it.

landing in this context is a lot easier than taking off, if you have an aircraft like a Cub that's capable of extremely short landing distances.

As noted in my answer, O'Brien also performs a take-off, at around 1:50 in the video. Of course, doing this with a Cub is something entirely different than with a larger/heavier craft. The question, however, was asking about 'an[y] airplane'.

While it’s not specifically a train, this tweet shows a float plane launched from the back of a trailer. The principle of launching from an unpowered, towed platform is similar to the scenario in your question.

As much as part of me wants to say, not a direct answer - delete, I have to admit that this is actually one of the most interesting videos I've seen lately. Nice find!

I was in doubt myself, but per jwzumwalt's comment indicating openness to "as close as it gets", an answer seemed more appropriate.

This type of Cessna stalls at ~60mph (less if it is light or in ground effect), so pulling the plane above 60mph is very easy.

The idea behind ZELL was to be able to disperse aircraft away from airfields, reducing the risk that the aircraft will be damaged in an attack on the airfield. Using rails misses the point of dispersal: you swap one easily identifiable, stationary target (airfield) for an easily identifiable, limited-movement target (train on rails).
You also have the problem that the size of rail cargo is severely limited by the loading gauge (i.e. the largest height and width of a rail vehicle). All obstacles around the track (overhead catenaries, signalling, tunnels, platforms) are designed to fit around this loading gauge. This means you have to remove the wings and tailplanes from your aircraft when you move the train, increasing reaction time.
It's much easier (and you get a much larger selection of hiding places) to hide a lorry with an assembled aircraft on top than to hide a train with same.
You also get a much larger selection of suitable roads to travel on.


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Does the safe taxi distance vary behind jet types for light aircraft?
It would seem a light aircraft taxiing behind a business jet could be closer than a B747. Perhaps there is a law (country or international) regulating power setting of a jet taxiing.

One authors recommendations.
Is there any rule of thumb for taxing behind jets based on size or type?

FWIW, back in the 1990s on 747-100/200 aircraft, we had no rules insofar as power setting during taxi for the simple reason that we always taxied at idle power with all four engines running. Even then the aircraft would accelerate to greater than the max taxi speed, which was 25 knots at the two 747 carriers I flew for. The only concern about distance from an aircraft in front of you was that the closer you got, the more you'd smell the exhaust. If interested see http://terryliittschwager.com/flying.php#taxiing747 for more info on taxing a 747.

A 747 behind another 747 isn't probably going to have any issue regardless of power setting. A C-152 behind a 747 is a different issue. What kind of aircraft are you asking about (doing the following)?


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HSI KG 525 PNI non slaved or only slaved?
I'm in Germany and currently on a project about the avionics of an older airplane (PA28). Here is a link to a former reddit question.
My Prof. and me want to update the Avionics now - he asked me to do a bit of research - it is quite a good exercise for me and i learn lot this practical way (i'll become an aircraft engineer)!. I do the prework for our maintenance company and they'll supervise my work/planning.
The main idea is to install new:

Garmin GNS430
Garmin GMA340
Insight G4 + Sensorics
Becker AR6203 22
KI - 525A or Garmin G5 DG/HSI
Insight G4 for experimental stuff (UAS courses with our piper)

This avionic stays, but will be reconnected

KN53 (with GS) – goes to KI 204
KI 204
KAP 100 (AP)

Will be removed:

GPS150
KI 203 - Insight G4 will come here instead
KN53 (w/o GS)
KY 196 (2x COM)

Right now i have the DG - KG107 in it, but my professor wants to update it to a HSI..

Now the question is if a KI-525A has a built-in gyro or is there only the possibility to connect it with the KG102 (which we dont have)?
I would like to have the new Garmin G5 DG/HSI but it seems that it doesn't have an EASA STC. Garmin is kinda quiet.  What do you think - should we install the G5 (DG/HSI) and hope for a STC or pick another HSI (maybe Century)

EDIT: Took 3 questions off the topic

Don't install non-STC'd equipment in your aircraft, it may be a very expensive mistake, who knows when/if Garmin will STC your aircraft. What country is this for, I'm guessing US?

Welcome to aviation.SE! You should consider splitting your question since you are asking multiple things at once. Also you have the ability to edit your question if you need to change anything. You can read the How to ask for some more details on how to post a good question on this site.

@Ron Beyer Its in Germany (EASA). Why would you guess US? Is my english so non-british :-D? Yeah i would neither like to do it..

@JimyPP I could not post more then 2 links.

A well written and documented question. I hope that you may receive a useful answer here.

The G5/430 combination was approved by EASA back in February! No reason why you can't use it. Some advice for you, learning how to use Google search is an invaluable skill for any aircraft engineer. :)

The G5/430 is not the issue. It's the DG/HSI Combination which is not approved by EASA. Like i read earlier and like i read now this article says that it is approved only as an attitude indicator aka Flight Instrument.
I honestly know how to google but sometimes i would like to hear new opinions on a topic.
I'll paste the official answer from Garmin sooner or later this day

I didn't read it that way. It says that it can be installed in the place of the primary attitude indicator but does a lot more than that.

To clarify, I read the press release as telling you -where- to install it, but not what it is authorized to do. Looks like the G5 can also be a flight director, which is pretty cool, and makes sense given the features of the 430 and 430W. BTW, don't forget the 430 can be upgraded to WAAS. That adds a huge benefit when flying any kind of approach. Long time ago, I reviewed the Garmin IQ3600 based on the PalmPilot for Aero-News w/a WAAS receiver. On the ground, it could point to exact house numbers!

@JuanJimenez That bit about learning to use google is patronising. Why are we all here?

@Koyovis Among other things, to learn what resources are available to engineers to do their jobs. If you don't know why you are here, I can't help you with that.


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Is there an FAA regulation to switch off the air-conditioning during take off?
The warning above the big white switches in the following picture had me intrigued. Is there some FAA regulation related to the same?

That placard is one way of handling CRM...

@fooot: I am asking about any related FAA regulation. Look at the two white swtiches and the text above that. The red placard is someone having fun i guess

Evidently it's a Piper Archer.

There's also usually a microswitch in the throttle that turns off the a/c when the throttle hits the top of the lever range.

AC sucks power out of the engines, just like in a car.

The power loss from AC is worse when you misspell the word "ensure".

Between the "Don't Touch Anything", "Kepp your mouth shut", and the use of "insure" instead of "ensure", I'm inclined to believe this is either a fake picture, or a tragically bad airline.

@erdekhayser This is a GA airplane, not an airliner. It's a single crew aircraft and the "co-pilot" would usually be a passenger (or a flight instructor...)

The operative regulations are those requiring compliance with aircraft placards.

Insure is a perfectly ordinary spelling of the word used in this photo, @Erdekhayser. Compare insure and ensure, and see the synonym discussion on both those pages.

-1 bc the proper checklist should be "1. don't touch anything 2. don't say anything"

It is not an FAA regulation to have the air conditioning off during takeoff and/or landing, however some manufacturers require it, in which case the pilot is legally obligated to comply with it.
I have flown two aircraft (both jets) which required it to be off:

Some of the Learjets require the AC to be off for both takeoff and landing because it uses a high draw electrical motor to drive the compressor, and when it cycles off and on it causes electrical spikes which can cause problems with the anti-skid system.
Some of the Dassault Falcon jets require the AC to be off for takeoff (actually, they automatically turn it off, but if the automatic system is inoperative the MEL requires turning it off manually) for performance reasons.  Since the AC is these aircraft is using bleed air off of the engine compressor as a source, allowing the air to continue through the engine instead increases thrust.

I know that many airliners have the option to takeoff with it on or off for performance reasons, and provide performance charts or adjustments for both.

As far as I know there is no specific regulation covering Air Conditioner operation however this varies from aircraft to aircraft and you should always check your specific aircrafts POH for information on systems installed and how they are to be operated.
In specific regards to the Piper Archer (pictured here) the POH states

On air conditioned models, the air conditioner must be “OFF” to ensure normal takeoff performance.

In terms of why that is there, Air Conditioner units use engine power to run (they are basically heat pumps). In smaller aircraft, especially on the slower/low power end of the spectrum (like the archer pictured here) taking away HP to run an AC unit can mean the difference between clearing a 50ft obstacle and not clearing it.
As for FAA regulations, the FAA does outline procedures for certifying a plane for reduced thrust takeoffs, however this involves power setting alterations. Depending on how you look at it running the Air Conditioner is in a way a reduced power takeoff however since you cant specifically adjust Air Conditioner power draw (as far as I know) running it could draw an unknown and potentially variant amount of power.

The same is true for landing, in case a go around would be required.

I'm pretty sure I remember seeing a similar statement in the POH for the Cherokees with A/C, too (not that the ones I've flown actually had A/C...)


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What are the pros/cons of ram air turbines?
Commercial aircraft are equipped with ram air turbines that can be deploy to provide power in case all other sources of power are lost. Ram air turbines have the benefit of providing power as long as the aircraft is moving through the air. However, aircraft are almost always designed with internal generators, driven off of the engines.
There is a limited case of adding generators to older aircraft. But they are also used to power large accessories, like the jamming pods on the EA-18 Growler. The EA-6B, which the Growler replaced, was also a modified attack aircraft using jamming pods with ram air turbines. Larger aircraft that are modified for the electronic warfare role don't seem to go this route though.
Obviously the turbine will add drag, and it seems like internal generators are more efficient, since almost all aircraft are designed to generate power that way.
So my question is: what are the benefits or drawbacks of using ram air turbines to generate power? While they are generally saved for emergencies, what makes them more useful in cases like jamming pods, compared to other options?

One obvious drawback as the sole source of power is that they don't generate power when the aircraft isn't moving through the air. And presumably would generate very little at taxi speeds.

I made a comment on TomMcW's answer, but I think it deserves to be an answer:
I think the answer lies in your question:

The EA-6B, which the Growler replaced, was also a modified attack aircraft using jamming pods with ram air turbines. Emphasis and links mine

If they were designing an electronic warfare aircraft from scratch, I'm sure that all the electronics would be powered by generators driven by the main engine(s). These engines would be sized to provide appropriate thrust for the expected mission profile and have excess capacity to provide power for the electronics.
However, since they are modifying existing aircraft for a new role they've found there is not enough excess capacity in the existing engines for the expected flight regimes and electricity generation, so dealing with the extra drag from the RAT is a cheaper and more expedient alternative than re-engining the the FA-18 (or the A-6 before it). Also, the cables needed to bring the power from the generator to the wing station must be added, and in tightly packed combat aircraft the space might not be there to add the wiring later. The RAT-driven pod only needs to be hooked up to a communication bus and brings its own power, so it can be designed once and used in a variety of aircraft. Multi-function displays in the cockpit just need a software upgrade, and the aircraft can perform reasonably well in its new role.
Addressing the recently added text about larger aircraft not needing the RAT:
The E-3 Sentry (for example) is powered by the CFM56-2 producing 18,000-34,000 pounds of thrust while the 707 it was based on was powered by the P&W JT3D-3B produced only 18,000 pounds of thrust. Per Wikipedia, the E-3 used CFM56-2A-2 version producing 24,000 pounds of thrust, thus it had the power for its normal flight regime plus power to spare for all the extra electrical demands of its electronic warfare role.

This is a good point and that's why I brought it up. I'd like to know a bit more detail... what might the limiting performance requirements be? How does it work out that added drag of a RAT is better than reduced power for more generator capacity? Larger aircraft tend to use generators so it seems to be something specific to the size and role.

@fooot - Paging Dr. Kämpf. Dr. Kämpf to the red courtesy phone. The specifics on that seem to be much more up his alley than mine. You may have noticed that my answer was full of vague generalities - there was a reason for that... :) Though I appreciate that someone gave me an upvote!

@fooot Just making presumptions here but to generate more power you'd first need a bigger generator. Then to drive the bigger generator will require more bleed air. As peter commented on my answer you'd have to accommodate the higher bleed air requirement with a more powerful compressor. To do that you'd probably have to either make the spools larger or add stages. I'd bet space in an F/A-18 is at a premium so you'd not only have to redesign the generator and the engine but possibly the airframe to fit it in. At some point you'd have a new plane.

@TomMcW - that's exactly my point about the EA-18 & EA-6B - they were modified from existing platforms, and the engine upgrades necessary to provide the additional electrical power were deemed more expensive/time consuming/etc than the additional drag of "slapping on" a RAT for the power.

Excellent addition, thank you Peter

You have kind of answered your own question. The down side to ram air turbines is they cause drag.
The up side is that they provide power outside the internal generating capacity of the aircraft (e.g., in emergencies when there is no power).
In the case a of a jamming pod, having its own power source eliminates/reduces the need to rely on internal power. That makes the pod modular. If the pod did not generate its own power, there would need to be a generator inside that sits there regardless of whether the pod were attached.

I don't quite understand your last paragraph. Presumably the plane the pod is attached to already has a generator so having an "unused" generator sitting in the plane doesn't seem to be much of an issue since it's not unused. Conversely, having a generator in the pod that's unused when the pod isn't fitted hardly seems to be a problem, since the whole pod is unused when it's no fitted! So, presumbaly, the problem is that the plane's generator can't supply enough power for the pod and that a fuel-powered generator within the pod isn't feasible for other reasons.

@DavidRicherby: Jamming needs lots of power. Your assumptions are correct, adding the capacity outright is not sensible and a RAT is a simple way to create the needed over.

How big is the benefit of not relying on an aircraft power source? It probably improves the aircraft when not carrying the pods, but pictures seem to show that the aircraft isn't often without them.

@fooot, the advantage lies mainly in simplifying the conversion as they don't have to replace the engine generator and don't have to run additional wires to the wing hardpoints.

Another advantage to a RAT as opposed to using the engine powered generator is that it reduces the requirement for bleed air so the engines can be more efficient and responsive.

Hmm - what is the more responsive engine good for when the RAT adds so much drag? It is really about the efficiency, because pulling all that power from the engine will shift its compressor far away from the design operating point.

@PeterKämpf I think that's what I'm trying to say. If you pull too much bleed air out the engine will run less efficiently. With a less efficient engine you have less reserve power. As far as overall efficiency of adding a RAT vs designing the engine around a bigger bleed requirement the later would seem to be more efficient. If the RAT was more efficient overall I think we'd see use of them on commercial aircraft.

Some of the engine efficiency v RAT efficiency trade off is likely due to the fact that an existing combat aircraft (A6, FA18) is being converted into an electronic warfare aircraft. In its new role, it's probably much more economical and easier to add a RAT than re-engine the aircraft to provide the extra power for the new electronics.


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Fuel jettison in Top Gun, is there any reason to do this other than show-boating?
20 years of watching Top Gun and I only noticed this today, after almost an annual repeat!

At 00:29 in this video, you can see what seems to be condensation swirling in the wake vortices.

Up until today, I thought this was just a cool shot catching some serious condensation under a high-G maneuver. However, if you look closely, you can see that it's actually a fuel jettison! At 00:38, it's very obvious.
I'm guessing that this is nothing more than show-boating and it sure did produce a cool shot.
Fuel jettison/dumping is used to reduce landing weight in emergencies but, is there any tactical/ops reason to do this?

I've watched Top Gun enough times that I can recite the dialogs of the whole movie, but I never noticed that!

I didn't think it was a dump, I always thought it was a smoke generator.

@GdD It's hard to tell, but a smoke generator would make more sense.  Also see this question.  I'm going to leave it for a few days, but it does seem that it was done "just because" - which I'm cool with :)  Jester's dead.  Yee hah!

Doesn't look like it was any 'tactical' reason- rather it was used to get a cool shot, which is totally OK with me. From rulit.me:

While setting up for a filming pass, the camera crew had difficulty spotting the gray F-14 against the mountainous background. Over the radio, Rat asked the pilot to blip the fuel dump switch and make a mini-cloud. The resulting effect of the atomized fuel swirling in the Tomcat’s vortices looked so good that this technique was used several times in the finished film.

I think they're talking about this scene:

Image from youtube screenshot
Looks like they used this technique to frame the aircraft against featureless mountains, sky etc.
Note: The site seems to have taken the quote from Topgun Days: Dogfighting, Cheating Death, and Hollywood Glory as One of America's Best Fighter Jocks by Dave Baranek.

Good find! Thank you.  That looks definitive to me.

Short answer: it’s not done in real air to air engagement, but it looks really cool on film. While it is common for pilots to jettison external tanks and other ordnance prior to getting into a merge to reduce weight and increase maneuvering limits, you will not dump internal fuel.  That’s pure energy, time and options to a pilot in a dogfight.
You have to remember Top Gun and other entertainment products are designed for their aesthetic and buy appeal more so than pure realism.  Most of the ‘dogfights’ are aircraft flying in formation, then carefully edited to look like an ACM engagement.  And a little bit of knowledge about how to make movies also comes into play here. Scenes and shots have to be framed in a 16 x 9 aspect area which, when projected onto a widescreen allows an aviation illiterate audience to ‘know’ what’s going on.  They also will commonly used scenes that have psychological cues to other things. In the scene you’re talking about, the F 14 dumping fuel looks something like a boxer losing his robe as he smashes his gloves and comes out of the corner of the ring ready to fight.  This is also enhanced by actor Michael Ironside’s dialogue as Jester giving a preflight description of the training exercise ie “Gentleman, this is your first hop….”, something like the ref at a fight calling the start of a round.  Some scenes in that movie are laughably unrealistic such as the hangar classroom scene which bears absolutely no resemblance to to any NFWS Topgun classroom setting; it’s more based on the high school ethos and the ‘Who’s hot for Teacher?’ vibe between Maverick and Charlie.  Again far more relatable to with your average moviegoing audience than the spartan classrooms in double wide trailers that the real Topgun used at that time.

I am 4 years late but kind of bored. This was mostly just for show, but fuel jettison (just like weapon jettison) has some tactical use. Reduced weight creates a higher TWR meaning more acceleration, as well as more maneuverability. It would be a waste of time tbh that you could use setting up for the merge and getting ready for the fight, but if you are desperate it could be a last resort, and possibly even a countermeasure against radar missiles as liquids do have a big impact on radar similarly to chaff.


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What is this thing sticking out under the F-22 Raptor's fuselage?
I was looking through some pictures I took of the Lockheed Martin F-22 Raptor performing a demo flight at Oshkosh 2023 and I noticed this thing sticking out from the bottom of the Raptor's fuselage. Could anyone please tell me what it is and what its function is?

As shown in the answers here: https://aviation.stackexchange.com/questions/82365/if-stealth-aircraft-are-invisible-to-radar-then-how-does-their-own-air-force-ma/82379#82379 , that is a Radar Reflector.

Does this answer your question? If stealth aircraft are invisible to radar, then how does their own Air Force manage them or see them in flight?


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What's the point of using T-38 to instill flight proficiency in Space Shuttle pilots?
As discussed in this Q&A, NASA pilots had to fly 15 hours a month on T-38 to maintain flight proficiency.

NASA Dryden's T-38 Talon trainer jet in flight over the main base complex at Edwards Air Force Base. Source
As a newbie, this seems rather weird - from all little I know about the Shuttle, its flying characteristics in no way resemble T-38.
So why use T-38? (or any normal jet at all)?

For the most part, flying is flying. The more you do it, the better you'll be. 15 hours a month (180 hours a year) in a high-performance supersonic jet is going to polish the hell out of your skills, albeit not necessarily those immediately applicable to the Shuttle.

See e.g. page 76 of "Excerpt from Astronaut T-38 Space Flight Readiness Training Syllabus". If you read pages above and below, you will have a good idea of the benefits of the training, and examples of situations recovered thanks to this proficiency. See also: Nasa's T-38 Operating Procedures

Training on T-38 was already required for Gemini and Apollo missions. Actually the first astronaut to die was during a T-38 accident in 1964 and sadly other would follow.

What the T-38 airplane provides NASA is currency and proficiency in high performance aircraft operations in a jet which has many of the same characteristics as the shuttle in this respect ie high wing loading, high approach and landing speeds, similar glide descent ratios.  The White Rocket is a temperamental and challenging little jet to land and will not tolerate sloppiness from her flight crew here.  She requires the pilot to stay well ahead of it while making an approach, plan out and execute small corrections very precisely while maintaining airspeed, glide path and angle of attack.  Maintaining good proficiency in these aspects of high performance aircraft flight and keeping sharp on that high speed mindset comes in handy in an astronaut's line of work.
And T-38s make excellent chase aircraft, capable of keeping up with the shuttle during the final phases of its descent and approach, and can provide an extra set of Mk 01 eyeballs to verify external functioning of systems, eg landing gear, speedbrakes, hydraulic leaks, etc.
Actually, outside of the shuttle sims, landing approach practice was done in a modified Gulfstream II which included a replica of the shuttle flight deck for the left seat guy.  It apparently was remarkably similar to the shuttle in a deadstick landing.

So, why isn't ALL flight training done in Gulfstream II?

In order to simulate the aerodynamic sleekness (ahem) of the "flying brick", the Gulfstream was actually flying with landing gear deployed and full reverse thrust. That's not something you want to do on a regular basis, otherwise you'll find yourself minus one Gulfstream pretty soon.

Actuall the G-IIS has a modification to its landing gear control system with an additional mode allowing only the main gear to extend.  It does not use thrust reversing during practice approaches.

@DVK not all training was done in the STA (shuttle training aircraft) for several reasons. NASA had dozens of T-38s, and only 4 STAs. The T-38 can simulate higher G-forces than the STA. T-38s share common maintenance and training practices with the Air Force, and may have been slightly cheaper to operate. STA requires a two-pilot crew, whereas the T-38 only requires one pilot. The T-38 was faster and more maneuverable, making it a better chase plane. Probably other reasons I'm not thinking of.

The biggest reason though, is probably that the T-38s date back to the early days of the astronaut corps - long before the shuttle was ever designed. There was never any reason to stop using them.

The STA absolutely did use reverse thrust on practice approaches, though I don't think they used full reverse as @Jörg suggests. There are many sources that talk about it. Here's one example: "... we lower the main gear of the STA and put the engines in reverse thrust," he said. "You know when a commercial plane lands and you're thrown forward after the wheels touch down? We do that at 30,000 feet."

@BretCopeland from that article: '"Astronauts only get one try to land the Shuttle; it lands as a glider," said Research Pilot Triple Nickel'. Really? The pilot's name is Triple Nickel? He's got the coolest parents in the world!!

I flew the T-38 in pilot training. (They ended Vietnam and tossed most of us out before we could finish since they no longer needed pilots.  Which also means I am now officially old.)
Reasons to use a T-38 for NASA.

The T-38 is a HIGH performance aircraft designed to be a  to see if trainees could handle that type of plane. And to also emulated performance fighter plane so you got high performance training.  They later made a fighter out of it - the F-5 and the current Navy F/A-18 is based on the T-38 design, so it was a high performance fighter type plane. Also the XF-17 and the F-20 were based on T-38s.  There is even a little T-38 in the new F-35. Great, great design.
When I was in, the T-38 had the 2nd highest angle of attack landing (nose up very high) of any jet in the history of the U.S. Air Force - with the by then obsolete B-58 bomber the only plane with a higher angle - MUCH like how a Shuttle lands very high nose up.
While you can probably refuel at any USAF base, you usually want to refuel at a base which knew your aircraft for qualified inspections/service and repair if needed.  When I was in (1972-73), there were 10 T-38 training bases, all except 1 located between South Georgia and Texas. (1 was near Phoenix.)  Most of the astronaut flying was between Houston, the home of the astronauts and Cape Kennedy, the launch point.  So on those flights, you could land at 9 bases to properly refuel and get service. When the NASA T-38s would land for service at most training bases, they would always give the students a "show" by doing a very fast climb after takeoff.  At one point the T-38 held the world time to climb record - over all the real actual jet fighters in the U.S., the Soviet Union and every other country.  It is a performance plane. The F-4 took many, many attempts and special modifications before it could barely take the record from the T-38.
MOST IMPORTANT.  Throw out everything else, the T-38 was designed to be a high performance plane the was CHEAP (compared to other jets planes) to fly.  Very low maintenance cost (1/3 of the design team were USAF mechanics) and quick turnaround (most training T-38 flew 2-3 missions a day.  Compare to say the B-38 which usually flew at most 1 time a week due to high maintenance time). Cheap and quick turnaround were requirements of a training aircraft. For NASA, that means you could get in much more training for your budget $$ and quick turnaround meant fewer planes were needed to train more astronauts.

Besides training, the T-38 is still used today as one of the primary chase planes when testing new aircraft, since at least during much of the testing it can keep up with the newest faster aircraft yet has 2 seats for a pilot and observer or fly's well with just a single pilot. At one time, the F-5 version of the T-38 was used as the enemy fighter at both the USAF and Navy TOP GUN schools (it's was used in the movie). So in proper hands, it can go head to head with F-14, F15, F16 and F-18 fighters. No bad for a "mere trainer". Its fast, maneuverable yet cheap.  Nothing comes close for the NASA mission.

And it also provided for routine basic transportation for the astronauts.  They got those monthly hours flying all over the country. Sometimes it was between NASA centers for meetings and other times to various places for PR purposes.  In the Shuttle era, mission specialists ode around in the back seat. Better than flying coach.

The general idea is to keep the pilot thinking like a pilot. Even ordinary pilots have to have 3 landings in the previous 90 days before they can fly with passengers. It's like warming up before playing tennis; you have to be doing it to stay in the groove.
Just like the first few balls you hit after not playing tennis for a while go over the fence, you can do some pretty crazy things in a plane if you are not tuned up. I once saw a guy jump in a high performance glider for his first flight of the season after doing a very minimal checkout and he misjudged the approach and ended up in the trees.
The choice of a T-38 is obviously because that is the standard AF trainer, but you are right, it is weird. The mentality of AF jocks is jets, jets, jets. But you are right that the Space Shuttle is not anything like a jet, so the T-38 is not the best choice of practice platform.
A better practice platform would be to use a glider and then weight it so it comes down like a rock. If NASA modified the glider the right way it could be made so that it would fly its approach like the shuttle. That would be a far more apropos way to keep the shuttle commanders current.

Actually, a "glider weighted like a rock" glides just as well as when unweighted, except the optimum glide speed is faster. Of course if you keep adding weight, eventually you go fast enough to break the wings off, but that's the reason that in competitive gliding, the regulations give the maximum weight limit, but no minimum. Trying to land a glider (safely) at a slower speed than it naturally wants to fly is not the same situation as flying a plane with a worse L/D ratio.

@alephzero I am trying to explain the basic ideas to the OP without using a lot of jargon.

Jargon isn't the issue. The last paragraph gives the wrong intuition. It's not about weight, it's about L/D. Gliders have a high L/D ratio, which would make them a terrible choice for simulating the shuttle's low L/D. An airplane modified to create more drag, such as the STA, is a much better choice. Also, having engines means you can make several approaches without needing a tow - much more practical (and safer) than a true glider. Astronauts consistently said the shuttle flies exactly like the STA, so saying there was a better choice feels like unjustified backseat engineering.

May I ask what the heck is STA?

@AntonTropashko Shuttle Training Aircraft - see Bret's reply further up.

@BretCopeland A glider can have whatever L/D you want. With full dive brakes on, some gliders have an L/D of around 5 which is lower than most jets. By increasing the density of the glider ("weighting" it), the L/D can be reduced to whatever is desired. The larger problem is that the shuttle lands at something like 225 MPH and a normal glider lands at 40-70 mph. To increase the landing speed the glider will have to be custom built and made much more dense than a normal glider.

@BretCopeland Jargon is an issue because I did not want to start going into the details of L/D with the OP. I wanted an easy to understand explanation that did not involve complex aerodynamic theory. You even had jargon in your comment that another pilot did not recognize.

L/D = 5 is still slightly better than the shuttle. Again, I see no justification for claiming that a glider would have been a better test platform than the one NASA picked, and the one professional test pilots claim flew exactly like the shuttle. On the other hand, picking a glider would have required completely re-engineering it (as even you admit), and would be substantially more dangerous due to its speed and single chance at landing. So again, your last paragraph is misleading, at best.

Also note that the STA (shuttle training aircraft) didn't actually touch down on its practice approaches. The approach terminated when the commander's eye level was the same as it would be in a real shuttle landing. A real glider would actually have to land, which means it would either have to be quite big and land at a high angle of attack, or have crazy long landing gear, or it would have to land further down the runway after the approach terminated, probably requiring a transition to yet another flare maneuver, which further reduces the safety margin.

Shuttle astronaut Mike Millane's autobiography, Riding Rockets, suggests that the mindset of flying a fast jet is a big factor, rather than the precise flight characteristics:

NASA's simulators were great at preparing astronauts to fly the space shuttle, but they had one critical shortcoming. They lacked a fear factor. No matter how badly you screwed up, simulators couldn't kill you. But high-performance jet aircraft could. Flying the T-38s kept the pilots razor sharp in dealing with potentially deadly time-critical situations, something spaceflight had in abundance.

And as it happened, unfortunately, the T-38 did kill four astronauts in the 1960s.

Another reason for using the T-38 was simply logistics. Astronauts were required to travel quite a lot; their base was in Houston, but depending on assignments they had to visit contractors and other NASA facilities to participate in development, testing and training. By letting them fly themselves they could get to wherever they needed and logging flight time.
Flying from Houston to either coast takes a few hours one way, so this was a lot of time saved which would otherwise have been spent on additional training.